Glauber model for small system using anisotropic and inhomogeneous density profile of proton

TL;DR

This paper adapts the Glauber model with anisotropic proton density profiles to small $p+p$ collisions, successfully reproducing multiplicity distributions and estimating geometric and flow properties typically associated with heavy ion collisions.

Contribution

It introduces a modified Glauber model for small systems using anisotropic and inhomogeneous proton densities, extending its application beyond heavy ion collisions.

Findings

Reproduces charged particle multiplicity distributions at LHC energies.

Estimates collision geometry parameters like impact parameter, $N_{coll}$, and $N_{part}$.

Calculates nuclear modification factor and flow coefficients in $p+p$ collisions.

Abstract

Recent studies reveal that at high energies, collisions of small system like $p+p$ gives signatures similar to that widely observed in heavy ion collisions hinting towards a possibility of forming a medium with collective behaviour. With this motivation, we have used the Glauber model, which is traditionally applied to heavy ion collisions, in small system using anisotropic and inhomogeneous density profile of proton and found that the proposed model reproduces the charged particle multiplicity distribution of $p+p$ collisions at LHC energies very well. Collision geometric properties like mean impact parameter, mean number of binary collisions ($\langle N_{coll} \rangle$) and mean number of participants ($\langle N_{part} \rangle$) at different multiplicities are determined. Having estimated $\langle N_{coll} \rangle$, we have calculated nuclear modification-like factor ($R_{HL}$) in $p+p$ collisions. We also estimated eccentricity and elliptic flow as a function of charged particle multiplicity using the linear response to initial geometry.